I am 16 years old and I feel a stab in the chest, dark vision and ...

I'm 16 years old, about 2 years ago I felt a stab in the chest and my vision became dark and lost force when the stitches happened, but after a few days they passed. Today I felt the pain again, only stronger, and together a little breathing difficulty. I'm afraid to tell my parents about it ... Can this be serious? Should I tell them about it urgently?